IEEE Transactions on Electron Devices | 2021
A Study of Linearity of C-H Diamond FETs for S-Band Power Application
Abstract
In this article, we report a study on the dc and RF linearity performances of a hydrogen-terminated (C-H) diamond field-effect transistor. An atomic-layer-deposited Al<sub>2</sub>O<sub>3</sub> (ALD-Al<sub>2</sub>O<sub>3</sub>) based C-H diamond (100) MOSFET was fabricated and then characterized by dc-<inline-formula> <tex-math notation= LaTeX >$I-V$ </tex-math></inline-formula>, <inline-formula> <tex-math notation= LaTeX >$C-V$ </tex-math></inline-formula>, small-signal, large-signal, pulsed <inline-formula> <tex-math notation= LaTeX >$I-V$ </tex-math></inline-formula>, and two-tone inter-modulation characteristics. The typical transfer results suggest that the presented device achieves a maximum transconductance <inline-formula> <tex-math notation= LaTeX >$(g_{m-\\max}) \\times$ </tex-math></inline-formula> gate-voltage swing (GVS) product of 673.2 <inline-formula> <tex-math notation= LaTeX >$\\text{V}\\cdot $ </tex-math></inline-formula>mS/mm, which is a record value among single-crystal diamond FETs to the best of our knowledge. The improved <inline-formula> <tex-math notation= LaTeX >${g}_{m}$ </tex-math></inline-formula>-linearity in this work can be attributed to the enhanced mobility performance, and the extracted effective mobility (<inline-formula> <tex-math notation= LaTeX >$\\mu _{{\\mathrm {eff}}}$ </tex-math></inline-formula>) varies from 105 to 200 cm<sup>2</sup>/<inline-formula> <tex-math notation= LaTeX >$\\text{V}\\cdot \\text{s}$ </tex-math></inline-formula>. Furthermore, theoretical calculations reveal that the obtained high-performance <inline-formula> <tex-math notation= LaTeX >$\\mu _{{\\mathrm {eff}}}$ </tex-math></inline-formula> is mainly due to the low-density surface charged impurities (<inline-formula> <tex-math notation= LaTeX >${ \\approx } 3.7\\times 10^{12}$ </tex-math></inline-formula> cm<sup>−2</sup>) and the alleviated surface roughness scattering. Small-signal RF measurement shows that the drain current swing (DCS) of <inline-formula> <tex-math notation= LaTeX >${f}_{T}$ </tex-math></inline-formula> is as high as −434 mA/mm. Unexpectedly, the RF output power performance at 2.6 GHz suffers from the severe drain current compression under the RF input drive. The subsequent pulsed <inline-formula> <tex-math notation= LaTeX >${I}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation= LaTeX >${V}$ </tex-math></inline-formula> results reveal that the cause could be ascribed to the drain-lag trapping effect. Even so, the device still shows attractive IM3-to-Carrier ratio (-C/IM3) values in the linear region, which indicates that the diamond MOSFET is a prospective candidate for the RF linearity application.